Ventricular defibrillation threshold estimation

Abstract

Systems and methods are provided for estimating a patient's ventricular defibrillation threshold (VDFT). Stimulation pulses, which are of at least three different energy levels up to 2 Joules, are delivered to the patient's right ventricle during a window defined between an R-wave and a vulnerable period that follows the R-wave. Voltage potentials, induced in response to the delivered RV stimulation pulses, are measured at a location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest. Potential gradients are computed using the measured voltage potentials. The patient's VDFT can then be estimated by estimating, based on the computed potential gradients, the RV stimulation energy level that would be required to achieve a minimum acceptable potential gradient at the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest.

1. A method for estimating a patient's ventricular defibrillation threshold (VDFT), comprising:
 (a) delivering a plurality of stimulation pulses to the patient's right ventricle (RV), the stimulation pulses being of at least three different energy levels up to 2 Joules, wherein each said stimulation pulse is delivered during a window defined between an R-wave and a vulnerable period that follows the R-wave; 
 (b) measuring voltage potentials induced in response to the RV stimulation pulses delivered at step (a), at or near a location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, wherein the voltage potentials are measured between one or more pairs of electrodes of a plurality of electrodes implanted at or near the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; 
 (c) using the voltage potentials measured at step (b) to compute the potential gradients, induced in response to the RV stimulation pulses delivered at step (a), for the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; and 
 (d) estimating the patient's VDFT by estimating, based on the potential gradients computed at step (c), the RV stimulation energy level that would be required to achieve a minimum acceptable potential gradient at the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; 
 wherein the location within the patient's LV, where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, is the apex and/or posterior lateral wall of the patient's LV. 
 
     
     
       2. The method of  claim 1 , wherein the voltage potentials induced in response to the RV stimulation pulses are only measured at or near the location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest. 
     
     
       3. The method of  claim 2 , wherein at least two of the plurality of electrodes, implanted at or near the location of the patient's LV, are part of a same intrapericardial left ventricular lead. 
     
     
       4. The method of  claim 2 , wherein at least two of the plurality of electrodes, implanted at or near the location of the patient's LV, are part of a same coronary sinus transvenous left ventricular lead. 
     
     
       5. The method of  claim 2 , wherein at least one of the plurality of electrodes, implanted at or near the location of the patient's LV, is part of a different lead than another one of the electrodes. 
     
     
       6. The method of  claim 1 , wherein the minimum acceptable potential gradient at or near the location of the patient's LV, where it is predicted that a potential gradient response to RV stimulation pulses will be lowest, is a potential gradient value in the range of approximately 4 Volts/cm to approximately 6 Volts/cm. 
     
     
       7. The method of  claim 1 , wherein:
 step (a) includes delivering multiple RV stimulation pulses at each of the at least three different energy levels; and 
 step (b) includes determining, for each of the different RV stimulation energy levels, an average of the voltage potentials measured at or near the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest. 
 
     
     
       8. The method of  claim 1 , wherein step (d) includes:
 (d.1) extrapolating, based on the potential gradients computed at step (c), a best fit line representative of the potential gradient at or near the location of the patient's LV as a function of RV stimulation energy levels, where the best fit line extends to at least the minimum acceptable potential gradient; and 
 (d.2) estimating, based on the extrapolated best fit line, the RV stimulation energy level that is needed to achieve the minimum acceptable potential gradient at the location within the patient's LV where it is predicted that a potential gradient response to RV stimulation pulses will be lowest. 
 
     
     
       9. The method of  claim 1 , wherein:
 the stimulation pulses delivered in step (a) are biphasic pulses. 
 
     
     
       10. The method of  claim 1 , wherein at least three of the different energy levels used at step (a) are greater than 10 millijoules, but not greater than 2 Joules. 
     
     
       11. The method of  claim 1 , wherein the energy level of one or more of the of the plurality of stimulation pulses delivered to the patient's RV at step (a) is/are between 1 and 2 Joules. 
     
     
       12. A system for estimating a patient's ventricular defibrillation threshold (VDFT), comprising:
 a plurality of implanted electrodes, at least two of which can be used to deliver stimulation and at least two of which can be used to sense responses to delivered stimulation; 
 a shocking circuit to deliver a plurality of stimulation pulses to the patient's right ventricle (RV), using at least two of the electrodes, the stimulation pulses being of at least three different energy levels up to 2 Joules, wherein each said stimulation pulse is delivered during a window defined between an R-wave and a vulnerable period that follows the R-wave; 
 a sensing circuit to measure voltage potentials induced in response to the delivered RV stimulation pulses, at a location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, using three or more electrodes of the plurality of implanted electrodes, wherein the three or more electrodes are implanted at or near the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; 
 one or more processors to
 compute the potential gradients induced in response to the delivered RV stimulation pulses based on the measured voltage potentials, wherein the computed potential gradients are for the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, and 
 estimate the patient's VDFT by estimating, based on the computed potential gradients, the RV stimulation energy level that would be required to achieve a minimum acceptable potential gradient at the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; 
 
 wherein the location within the patient's LV, where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, is the apex and/or posterior lateral wall of the patient's LV. 
 
     
     
       13. The system of  claim 12 , wherein at least two of the three or more electrodes, implanted at or near the location of the patient's LV, are part of a same transvenous left ventricular lead. 
     
     
       14. The system of  claim 12 , wherein at least two of the three or more electrodes, implanted at or near the location of the patient's LV, are part of a same coronary sinus interpericardial left ventricular lead. 
     
     
       15. The system of  claim 12 , wherein at least one of the three or more electrodes, implanted at or near the location of the patient's LV, is part of a different lead than another one of the electrodes. 
     
     
       16. The system of  claim 12 , wherein the minimum acceptable potential gradient at the location of the patient's LV, where it is predicted that a potential gradient response to RV stimulation pulses will be lowest, is a potential gradient value in the range of approximately 4 Volts/cm to approximately 6 Volts/cm. 
     
     
       17. The system of  claim 12 , wherein the one or more processors
 extrapolates, based on the computed potential gradients, a best fit line representative of the potential gradient at the location of the patient's LV as a function of RV stimulation energy levels, where the best fit line extends to at least the minimum acceptable potential gradient; and 
 estimates, based on the extrapolated best fit line, the RV stimulation energy level that is needed to achieve the minimum acceptable potential gradient at the location within the patient's LV where it is predicted that a potential gradient response to RV stimulation pulses will be lowest. 
 
     
     
       18. The system of  claim 12 , wherein the delivered stimulation pulses are biphasic pulses. 
     
     
       19. The system of  claim 12 , wherein at least three of the different energy levels used are greater than 10 millijoules, but not greater than 2 Joules. 
     
     
       20. The system of  claim 10 , wherein the energy level of one or more of the of the plurality of stimulation pulses delivered to the patient's RV is/are between 1 and 2 Joules. 
     
     
       21. A method for estimating a patient's ventricular defibrillation threshold (VDFT), comprising:
 (a) delivering a plurality of stimulation pulses to the patient's right ventricle (RV), the stimulation pulses being >10 millijoules and ≦2 Joules, with one or more of the stimulation pulses being between 1 and 2 Joules; 
 (b) measuring voltage potentials induced in response to the RV stimulation pulses delivered at step (a), only at a location of the patient's left ventricle (LV) where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, using a plurality of electrodes implanted at or near the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; 
 (c) using the voltage potentials measured at step (b) to compute the potential gradients induced in response to the RV stimulation pulses delivered at step (a), wherein the computed potential gradients are for the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest; and 
 (d) estimating the patient's VDFT by estimating, based on the potential gradients computed at step (c), the RV stimulation energy level that would be required to achieve a minimum acceptable potential gradient at the location of the patient's LV where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest. 
 
     
     
       22. The method of  claim 21 , wherein each said stimulation pulse delivered at step (a) is delivered during a window defined between an R-wave and a vulnerable period that follows the R-wave. 
     
     
       23. The method of  claim 21 , wherein the location within the patient's LV, where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, is the apex of the patient's LV. 
     
     
       24. The method of  claim 21 , wherein the location within the patient's LV, where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, is the posterior lateral wall of the patient's LV. 
     
     
       25. The method of  claim 21 , wherein the location within the patient's LV, where it is predicted that potential gradients induced in response to RV stimulation pulses will be lowest, is the apex and/or the posterior wall of the patient's LV.